1. Field of the Invention
The present invention relates to methods for displaying and manipulating multi-layer data displayed on a three-dimensional object.
2. Background of the Invention
Determining properties of a subsurface earth formation is a critical element in maximizing the profitability of oil and gas exploration and production. In order to improve oil, gas, and water exploration, drilling, and production operations, it is necessary to gather as much information as possible on the properties of the underground earth formations as well as the environment in which drilling takes place. Thus, well logging typically produces a large amount of information that needs to be analyzed to provide insights into the formation properties. The data to be analyzed are typically derived from logging operations using different instruments to probe various geophysical properties. Each of these instruments may generate an enormous amount of data, rendering analysis difficult. In addition, it is often necessary to compare and contrast data from different measurements to gain insights into the formation properties. Accordingly, a method that facilitate such comparison is desirable.
For example, neutron tools are often used to provide information on formation porosity because formation liquids in pores interact with neutrons. However, both water and hydrocarbons produce signals in neutron measurements. As a result, neutron logging data by themselves cannot reveal which pores contain water and which contain hydrocarbons. On the other hand, resistivity tools can easily differentiate whether a formation fluid is water or hydrocarbons, due to the high contrast in resistivity/conductivity in these two types of liquids. A combined use of these two measurements can readily provide information as to which pores contain hydrocarbons. In order to derive useful information from various formation logging data, these measurement data are typically presented in strip charts (“tracks”) and aligned side by side for analysis.
FIG. 1 shows a typical prior art method for presenting a plurality of logging data side-by-side tracks for analysis. The presentation shown in FIG. 1 is a standard format prescribed in, for example, Standard Practice 31A, published by the American Petroleum Institute, Washington, D. C. In this example, tracks 50, 54, 56 each include a header 57 which indicates the data types corresponding to curves 51, 53, 55, 59 presented in each track. Well log data are typically recorded with reference to the depth of the well. A depth ruler 52, which shows the measured depth (MD, the depth from the top of the well) of the data, is typically included in the graph as shown in FIG. 1 to provide a representation of the well.
Curves 51, 53, 55, 59 shown in FIG. 1 may include “raw” data recorded by well log instruments (e.g., detected voltages, detector counts, etc.) or more commonly values of parameters of interest (e.g., gamma density, neutron porosity, resistivity, acoustic travel time, etc.) derived from the raw data. In addition, some of these data may have been corrected for environmental effects.
As shown in FIG. 1, curves 51, 53, 55, 59 in tracks 50, 54, 56 do not lend themselves to intuitive interpretation by a user. In addition, representing a well in one dimension (as a function of depth) may obscure valuable information that is dependent on the geometry of the well or the size of the borehole. For example, many logging measurements are sensitive to tool standoffs. As a result, borehole washout, rugosity, or a dog leg in a borehole would introduce artifacts into the measurement data that may not be detected if no information on the borehole geometry is available.
Furthermore, many logging instruments are capable of different depths of investigation (DOI), i.e., various distances (radial depths) from the borehole wall into the formation. For example, propagation type resistivity tools can be used to probe formation resistivities at different DOI by varying the operational frequencies. Similarly, nuclear magnetic instruments can probe the formations at different DOI by using magnetic field gradients. Measurements at different DOI may provide, for example, better images of the formation surrounding the borehole or provide information regarding drilling fluid or fines invasion into the formation. A one-dimensional representation of a borehole cannot provide a proper perspective of these three-dimensional properties.
Therefore, it is desirable to have apparatus and methods for displaying multiple data sets related to a three-dimensional (3D) object (e.g., a well trajectory) in a manner that facilitates analysis of multiple data sets related to the 3D object and permits a proper perception of a geometrical relationship between the data and the 3D object.